In this competing renewal application, the Principal Investigator proposes to study the vitreal pharmacokinetics of ganciclovir, foscarnet, and cidofovir, three antiviral agents used to treat cytomegalovirus. A relatively new procedure, microdialysis, will be used which has the advantage of measuring drug levels in a continuous manner. By using this approach and from the experiments that are planned in pigmented rabbit eyes, it will be possible to more thoroughly determine each drug's ocular kinetics than from using previously methods in which each time interval represented a different group of animals. In addition, the investigator proposes to determine physico-chemical and biological determinants that help to explain ganciclovir's distribution and elimination profile. From this information, the investigator plans to develop approximately eighteen prodrugs that in theory could optimize antiviral therapy by prolonging drug levels in the vitreous.